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Gippsland Basin, Southeastern Australia

By
P.N. Davis
P.N. Davis
Esso Eastern Incorporated
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Published:
January 01, 1983

Abstract

The Gippsland basin is located offshore southeastern Australia. It is a wedge-shaped graben, open to the east and bounded to the north and south by east to west trending fault systems. The eastern margin is arbitrarily defined as the limit of continental crust.

The formation of the Gippsland basin is directly related to the eccentric movement of the Tasmanian continental block relative to the Australian and Antarctic blocks during the breakup of Gondwanaland. Rotation of the Tasmanian block to the southwest created a tensional regime in which the Gippsland basin was formed by crustal thinning. This relative movement began in the mid-Cretaceous and ceased in the Eocene when the Tasmanian subplate became part of the Australian plate (Griffiths, 1971).

Initial sedimentation during the Early Cretaceous in the Gippsland basin consisted of a rift valley sequence of non-marine sandstones, siltstones, and shales. Following tilting and, in places, severe erosion at the end of the Early Cretaceous, continued extension and rotation activated a series of northwesterly trending normal faults in the area of the present day offshore Gippsland basin. During this period, the rapidly subsiding basin was filled with continental and marginal marine sediments of the Upper Cretaceous to late Eocene Latrobe Group. The normal faulting and rotation produced an overall wedge-shaped graben, which widened to the southeast and is bounded to the north and south by stable platform areas. Extension and normal faulting diminished markedly after the early Eocene and few faults continued into the late Eocene. From the early Eocene to the Miocene a series of northeasterly trending anticlines formed. Coincident with this folding was the reversal of movement on previously normal faults.

Several author (Richards and Hopkins, 1969; Threlfall et al, 1976) attributed this compression to right lateral transform movement on the east to west basin-bounding fault system. Rapid burial of the Eocene Gippsland basin sediments was effected by progradation of Oligocene to Recent shelfal carbonates onto a sagging continental margin. Submarine channelling due to eustatic sea level changes is prevalent through all the Upper Tertiary sequence.

Both of the above fault types are shown on Line A. The predominant faulting style is normal and down-to-the-south (type 1 on line A). The faulting intensity diminishes in the younger part of the section. One relatively large fault (at shotpoint 2560) continued through to post-Latrobe Group time. All of the normal faults shown on Line A belong to the northwesterly trending "basin forming" fault system.

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Contents

AAPG Studies in Geology

Seismic Expression of Structural Styles: A Picture and Work Atlas. Volume 1–The Layered Earth, Volume 2–Tectonics Of Extensional Provinces, & Volume 3–Tectonics Of Compressional Provinces

A. W. Bally
A. W. Bally
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American Association of Petroleum Geologists
Volume
15
ISBN electronic:
9781629810188
Publication date:
January 01, 1983

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